JB PARCELFloor Area Ratio Calculator
Floor area ratio is how zoning caps the total size of a building, every story counted. Enter the lot and the FAR limit to see how much floor area you can build, how tall it has to go, and what the land costs per buildable square foot.
How this calculator works
Floor area ratio is total gross floor area divided by lot area. Every story counts. A 30,000 square foot building on a one acre lot, 43,560 square feet, has a FAR of 0.69, whether it is one sprawling story or three stacked ones.
Run it the other way and FAR tells you what you can build. Multiply the lot area by the maximum FAR and you have the most floor area zoning allows. On that acre, a FAR of 1.5 allows 65,340 square feet.
How tall that has to be depends on the footprint you can actually achieve. Setbacks, parking, landscaping, and stormwater usually leave far less than the whole lot for the building. Divide the allowed floor area by the footprint, round up, and that is how many stories it takes to use the full FAR.
Developers use FAR to price land. Divide the land price by the buildable floor area and you get land cost per buildable square foot, which lets you compare a cheap lot with a low FAR against an expensive lot with a high one on equal terms.
Worked example: pricing a half-acre infill lot
A 21,780 sf lot zoned for a FAR of 2.0, offered at $900,000, where setbacks and parking leave room for a footprint of about half the lot.
| Most floor area allowed | 43,560 sf |
|---|---|
| Footprint at 50% coverage | 10,890 sf |
| Stories to use it all | 4 |
| Land cost per buildable sf | $20.66 |
If the height limit in that district stops at three stories, the real buildable area is 32,670 sf and the land cost rises to $27.55 per buildable square foot. Check height before you accept the FAR at face value, because the lower of the two limits is the one you build to.
Where the numbers come from
FAR limits and the definition of floor area come from each jurisdiction's zoning ordinance. Nothing on this page is the legal limit for a specific lot. Confirm the district, the FAR, the height limit, and the floor area definition with the planning department.
Questions investors ask
What is floor area ratio?
The ratio of a building's total floor area to the area of its lot. A FAR of 2.0 means you can build two square feet of floor area for every square foot of land, as one tall building or a shorter one covering more of the lot.
How do you calculate FAR?
Add up the gross floor area of every story and divide by the lot area. A 30,000 square foot building on a 43,560 square foot lot has a FAR of about 0.69. To find the most you can build, multiply the lot area by the maximum FAR the zoning allows.
What counts as floor area for FAR?
It depends on the ordinance. Most count the gross area of every enclosed story. Many exclude some combination of basements, parking garages, mechanical rooms, and stair shafts. The definitions section of the zoning code decides it.
How is FAR different from lot coverage?
Lot coverage counts only the footprint on the ground. FAR counts every story. A district can allow high coverage and low FAR, which produces low wide buildings, or low coverage and high FAR, which pushes buildings up. Check both with the lot coverage calculator.
Why do developers care about land cost per buildable square foot?
Because it is the fair way to compare sites. A $500,000 lot that allows 10,000 square feet costs $50 per buildable foot, while a $900,000 lot that allows 43,560 costs about $21. The cheaper lot is the more expensive land.
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Screening a real property? Pull its appraised value, assessed value, acreage, land use, and last recorded sale off the JB PARCEL parcel map and drop the real numbers into this calculator instead of guessing. Coverage runs across every county we carry.